Does Dry Pour Concrete Actually Work? A UK Guide
Published 30 July 2026 · Browse all tools
Dry pouring has had a big social-media moment. Short videos show someone tipping bags of dry concrete mix into a form, smoothing it off, hosing it down, and calling it done. It looks fast and it looks easy. The honest answer, which most of those videos skip: it can be fine for light, non-structural jobs, but it doesn't reliably reach a designed concrete strength. If you've decided it's right for your job, the Dry Pour Concrete Calculator works out your bags — but read this first, because for a lot of jobs the honest answer is don't.
What dry pour actually is
Dry pouring — also called dry pouring or pour-and-soak — means placing dry bagged concrete or ballast mix directly into a prepared form without adding water first. You compact it, level or screed it off, then wet it from the top with a hose or rely on ground and rain moisture to do the curing over the following days.
The difference from a conventional wet mix is fundamental. In a normal pour, water is added to the mix at a controlled ratio before placement, ensuring the cement paste coats every aggregate particle evenly and hydration starts uniformly throughout the mass. Dry pouring inverts that sequence — the mix goes in dry and water soaks in from above.
Takeaway: the method saves time on mixing. That's the only thing it saves.
Why the strength is the problem
Concrete strength depends on two things: the water-to-cement ratio (lower is stronger, down to a workable minimum) and complete, even hydration of the cement particles throughout the mix. Dry pouring can control neither.
Water penetrates from the top. In a shallow 50–75mm pour, it has a reasonable chance of reaching the bottom before the surface dries out. In anything deeper, the bottom of the pour can remain partially or wholly unhydrated — dry pockets that never harden properly. The result isn't one consistent slab; it's a gradient from harder at the top to weaker or dusty at the bottom.
The UK specifies structural and designed concretes to BS 8500 (the UK complement to BS EN 206) by compressive strength class: C20/25, C25/30, and so on. These classes describe guaranteed minimum strengths achieved under controlled mixing and curing. Dry pour gives you no verifiable strength class whatsoever.
Most "how to dry pour" content online shows the method working on a thin, small slab filmed shortly after placement — and stops there. It doesn't tell you the mix won't cure evenly at any real depth, won't reach a specified strength class, and won't be accepted by a UK building inspector for any structural application. Say it plainly: if you need a concrete strength class, dry pour isn't the method.
Takeaway: if the job needs a specified strength, wet-mix it. There's no shortcut around hydration chemistry.
Where dry pour is genuinely fine
There are jobs where dry pouring is a perfectly reasonable trade-off:
- Setting a single fence post in stable, well-drained ground (though ready-mixed Postcrete by Blue Circle is the usual UK choice here — it's formulated for the job)
- A small, lightweight garden shed base on compacted, well-drained ground with a shallow pour depth
- Bedding kerb edging or garden borders
- Filling small, low-consequence voids
The common thread across all of these: shallow depth (75mm or less), no structural or dynamic load, and low consequence if it fails. A crumbling shed base means re-doing the slab. A crumbling footing means far more.
Takeaway: if the consequence of failure is 'annoying', dry pour might be acceptable. If it's 'expensive or dangerous', mix it wet.
Where you should not use dry pour
Don't dry pour for:
- House or extension foundations — these are notifiable under Building Regulations and must meet a specified concrete strength class under BS 8500
- Garage or workshop bases that take vehicle loads or heavy racking
- Driveways that carry car traffic
- Footings for any outbuilding over the permitted development size thresholds
- Deeper pours (above 100mm) where the bottom section won't hydrate
- Cold or waterlogged ground conditions — frozen or saturated ground stops hydration entirely
If a building inspector will ever see the work, or if the slab carries any meaningful load, this isn't the right method.
Takeaway: the more the job matters, the more this method doesn't suit it.
Worked example — a small garden shed base in Leeds
A concrete base for a lightweight 8ft × 6ft garden shed in Leeds: 2.4m × 1.8m, 75mm deep, dry-poured with standard 20kg general-purpose bags from Wickes or Travis Perkins.
- Base volume = 2.4 × 1.8 × 0.075 = 0.324 m³
- Yield per 20kg bag = 0.009 m³ (standard for a 20kg GP mix bag)
- Bags required = 0.324 ÷ 0.009 = 36 → 36 bags (round up)
Use the Dry Pour Concrete Calculator to confirm this against your chosen product, since bag yields vary between brands and mixes.
Even for this low-consequence application, the honest caveat stands: a properly mixed wet pour at the same volume gives a more reliable, consistent base. The dry pour is the convenience trade-off — acceptable here because a lightweight shed is low-consequence, the depth is shallow, and the base can be re-done if it fails without wider damage.
Takeaway: know what you're trading. Speed for certainty. For a lightweight shed, it's an acceptable deal.
UK suppliers and the cost reality
Bagged ready-mix general-purpose concrete (the standard dry-pour product) is widely available from Travis Perkins, Wickes, B&Q and most builders' merchants. Expect to pay around £5–£8 per 20kg bag in 2026 depending on supplier and quantity. For the shed-base example above, 36 bags is roughly £180–£290 in materials before any delivery cost.
For fence posts specifically, Blue Circle Postcrete is the go-to product — it's a fast-setting formulation designed for the job, and most UK groundworkers use it for that one application without a second thought.
In practice, experienced groundworkers in the UK rarely dry-pour anything that actually matters. The time saved on mixing is genuinely small once you account for bag-by-bag placement, levelling and wetting. The risk that the base crumbles in two winters isn't. The trade saying is blunt: if it's worth concreting, it's worth mixing. That's not a rule against dry-pouring a shed base; it's a reminder that the convenience premium comes with a performance cost you can't inspect after the event.
Takeaway: budget for the right method, not just the fastest one.
If you still want to dry pour: do it properly
If the job is genuinely suitable and you're going ahead:
- Compact the sub-base first. Loose, uncompacted ground is the most common cause of a dry-pour slab failing — it settles under the concrete and breaks it. If you want to understand sub-base depth and compaction, this guide on sub-bases under concrete slabs covers it in detail.
- Keep the pour shallow. 50–75mm is the practical limit for reasonable hydration from the top.
- Wet slowly and thoroughly. Don't blast it with a full-pressure hose. A gentle spray or a watering can across the full surface, multiple passes, gives water time to soak through rather than run off.
- Mist it over the following days. Don't let the surface dry out before the cement has finished hydrating — especially in warm weather.
- Protect from heavy rain and frost during the initial cure. Both can disrupt the chemical process before it's complete.
Takeaway: even for the jobs it suits, the method rewards patience over speed.
What this means for your job
If the job is light, shallow and non-structural, dry pour is a reasonable convenience option. Use the Dry Pour Concrete Calculator to work out how many bags you need before you order.
If the job needs a strength class — foundations, load-bearing bases, anything under Building Regulations — mix it wet and use the Concrete Volume Calculator to size a ready-mix order or work out your aggregate quantities. The extra hour of mixing is nothing compared to the cost of re-doing failed structural concrete.